Re: [eclipselink-users] @OrderBy is not working

[Tom Ware <tom.ware@xxxxxxxxxx>]

HI Antonio,

  There is a subtlety about the way @OrderBy works that is causing your issue. 
 From the specification:

"The OrderBy annotation specifies the ordering of the elements of a collection 
valued association at the point when the association is retrieved."

  The key here is the phrase "when the association is retrieved".  In your 
case, when your find is executed, the association is still managed and no 
retrieval logic occurs.

  Try calling em.refresh(news).

  The bottom line is that @OrderBy does not provide any magic that manages your 
in-memory collections.  It is used only when SQL is built.

-Tom


Antonio Goncalves wrote:
> Hi,
>
> I have two entities : News has a list of Comment. I want my comments to 
> be ordered by posted date. So I used the @OrderBy annotation as follow :
>
>
> @Entity
> public class News {
>
>     @Id
>     @GeneratedValue
>     private Long id;
>     @Column(nullable = false)
>     private String content;
>     @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.PERSIST)
>     @OrderBy("*postedDate *desc")
>     private List<Comment> comments;
>     ...
> }
>
> @Entity
> public class Comment {
>
>     @Id
>     @GeneratedValue
>     private Long id;
>     private String nickname;
>     private String content;
>     private Integer note;
>     @Column(name = "posted_date")
>     @Temporal(TemporalType.TIMESTAMP)
>     private Date *postedDate*;
>     ...
>     public Comment() {
>     }
>
>     public Comment(String nickname, String content, Integer note, String 
> *postedDate*) {
>         this.nickname = nickname;
>         this.content = content;
>         this.note = note;
>
>         try {
>             DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
>             this.*postedDate *= df.parse(postedDate);
>         } catch (ParseException e) {
>             e.printStackTrace();
>         }
>     }
>     ...
> }
>
> As you can see, the postedDate is of type Date and @Temporal. I persist 
> a news with some comments. But when I return them, they are not ordered 
> by date. Is there anything wrong with this code ? I wrote a test case to 
> show what it should be doing : 
>
> @Test
>     public void createComment() throws Exception {
>
>         News news = new News("Death of Michael Jackson");
>         news.addComment(new Comment("gonzo", "Third comment", 1, 
> "2009-07-03"));
>         news.addComment(new Comment("elvis", "First comment", 3, 
> "2009-07-01"));
>         news.addComment(new Comment("gonzo", "Second comment", 5, 
> "2009-07-02"));
>         news.addComment(new Comment("elvis", "Fourth comment", 2, 
> "2009-07-06"));
>
>         tx.begin();
>         em.persist(news);
>         tx.commit();
>
>         tx.begin();
>         news = em.find(News.class, news.getId());
>         tx.commit();
>
>         assertEquals("Death of Michael Jackson", news.getContent());
>         assertEquals(4, news.getComments().size());
>         assertEquals("First comment", 
> news.getComments().get(0).getContent());
>         assertEquals("Second comment", 
> news.getComments().get(1).getContent());
>         assertEquals("Third comment", 
> news.getComments().get(2).getContent());
>         assertEquals("Fourth comment", 
> news.getComments().get(3).getContent());
>     }
>
>
> Thanks, 
> Antonio
>
>
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>
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